Pyrazinamide

Pyrazinamide is indicated for the initial treatment of active tuberculosis in adults and children when combined with other antituberculous agents.

• The current recommendation of the CDC for drug-susceptible disease is to use a six-month regimen for initial treatment of active tuberculosis, consisting of isoniazid, rifampin and Pyrazinamide given for 2 months, followed by isoniazid and rifampin for 4 months
• Patients with drug-resistant disease should be treated with regimens individualized to their situation. Pyrazinamide frequently will be an important component of such therapy.
• In patients with concomitant HIV infection, the physician should be aware of current recommendation of CDC. It is possible these patients may require a longer course of treatment

It is also indicated after treatment failure with other primary drugs in any form of active tuberculosis.

Pyrazinamide should only be used in conjunction with other effective antituberculous agents.

Anti-Tubercular Chemotherapeutics

Pyrazinamide may be bacteriostatic or bactericidal in action, depending on the concentration of the drug attained at the site of the infection and the susceptibility of the infecting organism. Its activity appears to partly depend on conversion of the drug to pyrazinoic acid (POA), which lowers the pH of the environment below that which is necessary for growth of Mycobacterium tuberculosis. Susceptible strains of M. tuberculosis produce pyrazinamidase, an enzyme that deaminates pyrazinamide to POA, and the in vitro susceptibility of a given strain of the organism appears to correspond to its pyrazinamidase activity.

Usual Adult Dose for Tuberculosis: Active:

15 to 30 mg/kg (up to 2 g) orally once a day in combination with three other antituberculous drugs for the initial 2 months of a 6-month or 9-month treatment regimen, until drug susceptibility tests are known. An alternate dosing regimen of 50 to 75 mg/kg (up to 3 g) orally twice a week may be used after 2 weeks of daily therapy to increase patient compliance.

Alternatively, the CDC, The American Thoracic Society, and the Infectious Diseases Society of America suggest the following dosing based on estimated lean body weight:

Daily dosing:

• 40 to 45 kg: 1000 mg
• 56 to 75 kg: 1500 mg
• 76 to 90 kg: 2000 mg

Twice weekly dosing:

• 40 to 55 kg: 2000 mg
• 56 to 75 kg: 3000 mg
• 76 to 90 kg: 4000 mg

Thrice weekly dosing:

• 40 to 55 kg: 1500 mg
• 56 to 75 kg: 2500 mg
• 76 to 90 kg: 3000 mg

Usual Adult Dose for Tuberculosis: Latent: 

A public health expert should be consulted prior to the use of the combination regimen with rifampin.

15 to 20 mg/kg, based on actual body weight (lean), orally once daily (maximum 2 g) for 2 months. Alternatively, a dosage of 50 mg/kg may be administered orally twice-weekly (maximum 4 g).

Usual Pediatric Dose for Tuberculosis: Active:

(Used as part of a multidrug regimen. Treatment regimens consist of an initial 2-month phase, followed by a continuation phase of 4 or 7 additional months. Frequency of dosing may differ depending on phase of therapy)

Infants, Children less than 40 kg and Adolescents 14 years and younger and less than 40 kg:
Non-HIV patients:

• Daily therapy: 15 to 30 mg/kg/dose (maximum: 2 g/dose) once daily
• Directly observed therapy (DOT): 50 mg/kg/dose (maximum: 2 g/dose) twice weekly

HIV-exposed/infected patients:

• Daily therapy: 20 to 40 mg/kg/dose once daily (maximum: 2 g/day)

Antagonises the effect of uricosuric agents (e.g. probenecid, sulfinpyrazone). May reduce the contraceptive effect of oestrogens. May inactivate oral typhoid vaccine. May increase the serum concentration of ciclosporin. May enhance the hepatotoxic effect of rifampicin.

Pyrazinamide is contraindicated in persons:

• With severe hepatic damage.
• Who have shown hypersensitivity to it.
• With acute gout.

General: Fever, porphyria and dysuria have rarely been reported. Gout.

Gastrointestinal: The principal adverse effect is a hepatic reaction. Hepatotoxicity appears to be dose related, and may appear at any time during therapy. GI disturbances including nausea, vomiting and anorexia have also been reported.

Hematologic and Lymphatic: Thrombocytopenia and sideroblastic anemia with erythroid hyperplasia, vacuolation of erythrocytes and increased serum iron concentration have occurred rarely with this drug. Adverse effects on blood clotting mechanisms have also been rarely reported.

Other: Mild arthralgia and myalgia have been reported frequently. Hypersensitivity reactions including rashes, urticaria, and pruritis have been reported. Fever, acne, photosensitivity, porphyria, dysuria and interstitial nephritis have been reported rarely.

Pregnancy Category C. Animal reproduction studies have not been conducted with Pyrazinamide. It is also not known whether Pyrazinamide can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Pyrazinamide should be given to a pregnant woman only if clearly needed.

Nursing Mothers: Pyrazinamide has been found in small amounts in breast milk. Therefore, it is advised that Pyrazinamide be used with caution in nursing mothers taking into account the risk-benefit of this therapy.

Overdosage experience is limited. In one case report of overdose, abnormal liver function tests developed. These spontaneously reverted to normal when the drug was stopped. Clinical monitoring and supportive therapy should be employed. Pyrazinamide is dialyzable.

Store between 15-30° C.

Safe

Pyrazinamide 500mg